Sclerosis of the arteries, myocardial infarction (or angio stenosis) and cerebral thrombosis and ischemic cerebral infarction are caused by choking or decreasing of blood flow due to stenosis formed in an artery, cerebral vessel and coronary arteries. Thrombosis is generated by clot on the blood vessel or inflammation of blood vessel and expansion or hardening of atheromatous plaques between the media and endothelium of arteries or blood vessels. Angiography is a well-known diagnosis to find clots, thromboses or plaques. A fine blood catheter is inserted into a blood vessel and injects contrast medium therethrough. The blood flow is observed by the flow of the contrast medium that is observable by X-ray, which is blocked by contrast medium and less-blocked by the human body of a patient. Catheters are usually percutaneously inserted through the femoral veins and are pushed up to the target portion of the veins or arteries. Then, the contrast medium is injected into the blood flow through the catheter. Since the contrast medium has less transparency against the X-ray, we can have a image such that the vein or arteries, of which a downstream vessel is narrowed or choked by clots or atheromasclerosis, is visualized by the shadow of X-ray such that the narrowed or choked vessel and the upper stream vessels are shown as shadowed areas, and the other body portions as unshadowed areas. By this evaluation method, it is possible to find vessels which have the narrowed or choked portions in their down streams and narrowed or choked vessel (i.e., Sclerosis) portion.
Once infarction is found and diagnosed as thrombus or sclerosis, thrombus dissolvers or stents installed in the blood vessels are used as treatment. Statin (a trade mark: HMG-CoA reductase enzyme inhibitor) is widely used for thrombus dissolver. Stents are cylindrical metal meshes and made from metal tubes. Stents can be expanded in the blood vessels by balloon catheters. Stents are used for the operation of thrombus and coronary disease. A stent is inserted in a balloon catheter in minimum-diameter state (i.e., shrunken state), or a stent made from a metal tube is inserted in the blood vessel with surfaces of the balloon catheter in a shrunken state and pushed into the blood vessel so that the diameter of the balloon catheter is of a minimum dimension. The catheter to which the stent is attached travels inside the blood vessels, and the balloon is inflated when the catheter reaches the infarction portion of the blood vessel. The diameter of the stent is increased by the expansion or inflation of the balloon. Therefore, the infarction portion of the blood vessel is pushed outwards by increasing the diameter of the stent so that infarction is cleared. The diameter of the stent is maintained by the inflated balloon. After the stent is inflated in the blood vessel, the balloon is shrunken to the original size and the image of the blood vessel is taken by using contrast medium and X-ray. By comparing two images of the blood vessel, such as that before and after the stent is inserted, it is confirmed whether or not the insertion of the sent has been properly carried out. If the image of the contrast medium flow in the position where the stent stays in the blood vessel has the same shape of the flow in other positions along the blood vessel, then it can be deduced that the stent is properly inserted and widened in the infarction portion of the blood vessel such that the infarction is successfully removed.